Since it is lightweight compared with glass, resin is used in very many optical fields such as optical lenses, prisms, optical fibers and various optical films. However, there is a problem that in a resin film, the strength of the film falls due to ultraviolet radiation, or transparency falls due to discoloration, and for optical film use, this problem has serious consequences.
For this reason, an ultraviolet absorber such as a benzotriazole compound or a triazine compound is used in an optical film. For example, JP,2002-249600,A (Claim 2, [0018]) [0029], [0031]) or JP,2001-324616,A (Claim 2, [0025], [0053], [0059]) disclose a norbornene resin film containing an ultraviolet absorber.
However, in the case of a prior art ultraviolet absorber, absorption is shifted to the low wavelength side. Since the absorption at 380 nm is low, ultraviolet absorber of a large amount, which gives the required absorbing power must be used, so bleed-out or a change of color tone could not be avoided.
JP,11-71356,A (Claim 1, [0009]-[0027], and [0042]-[0047]) disclose a triazine compound ultraviolet absorber, but there is no mention of an optical film.
Hence, an optical film containing sufficient ultraviolet absorber to have an ultraviolet absorption capability at a wavelength of 380 nm to make it suitable for an optical film, and with little bleed-out, had not yet been obtained.